Tuesday, 22 July 2014

"Many, if not most, particle physicists despised nuclear physics"

My recent post mentioning Skyrmions has prompted me to walk down the corridor to get back my copy of Selected Papers, with Commentary, of Tony Hilton Royle Skyrme, which I bought on a whim when World Scientific were having a sale.  A quick search through my email reveals I bought 9 books at the time, all for £6 each.  I guess I thought it was a great bargain at the time, and actually I've made decent use of some of the books.  I don't suppose I'll ever open the 1200-page Sixty Years of Double Beta Decay but it may give me a bit of exercise next time I have to move offices.

Anyway, I thought I'd try to get better acquainted with the basics of Skyrmions, and it seemed like a good place to start.  I haven't got onto the real subject matter yet, but can't resist quoting this from the preamble to the commentary on the Skyrmion papers (which form one section of the book).  Penned by the editor, Gerald E. Brown, who died recently -- there is a special issue of Nuclear Physics A coming out soon in his honour (see here) -- it is written in an informal way discussing the history of the Skyrmion and its links with other field theory approaches to nuclei and nucleons.  He (Brown) says
I told [Feynman] that the MIT bag model of quarks was simply too large;  it had a radius R of ~ 1 fm. With such a large radius, the nucleons would be like grapefruit in a bowl.  It would be difficult to see how they could perform the independent motion that they exhibit in the shell model.

Feynman responded by a number of objections and penetrating questions, but he was obviously intrigued.  This was a great stimulation to me, since many, if not most, particle physicists despised nuclear physics.  (In fact the only criticism that I have of Sanyuk's article is that it tries to convert Tony Skyrme retroactively into a particle theorist.)  Feynman asked me how I wanted to compress the MIT bag.  I told him that the pion cloud would compress the quarks.  Only later, I discovered that in the Skyrme model, the pion cloud compressed the quarks to a point, the point source of the baryon number.

The underlining is mine.  The whole prologue is written in the same style -- the sort of freewheeling arrogance that big-name professors sometimes profess.  Quite a rollicking read, really.  But is it true? Do most particle physicists really hate nuclear physics?  It would explain a lot.



Tuesday, 15 July 2014

Graduation week - for me too

As I walked across campus this morning, I saw the sight of many people dressed up smartly, some in academic dress, for it is (undergraduate) graduation week at the University of Surrey.  Today, it's the Faculty of Health and Medical Sciences (aka FHMS).  My faculty ("FEPS" = Faculty of Engineering and Physical Sciences) is on Friday, and I'll be present at the afternoon ceremony to see our students graduate.  The other two faculties on campus presumably have their ceremonies tomorrow and Thursday.  One of these faculties, by the way, is now called "FBEL" = Faculty of Business, Economics and Law.  It used to be called the Faculty of Management and Law, with the abbreviation FML, which I'm sure caused much amusement to the students before it was deemed that it needed to change.

It can't really be denied that graduation ceremonies are a bit on the boring side, but for the period of the ceremony when the person or people you are there to see are graduating, it's actually rather nice.  I get to see the students who I worked with for their Final Year Projects, and taught in several other courses.  Students who were my personal tutees, students who I know struggled with problems of an academic and non-academic nature, now reaping the reward of their hard work and perseverance.  Occasionally I also see a student who I utterly fail to recognise and wonder why - perhaps because they studied more from books than from lectures or were unusually quiet, or didn't take my optional courses.  Indeed, now that our intake is the size it is, there will be some students who I will never teach, given the way the teaching allocation currently stands.

As I mentioned last year, and the year before, and the year before that,  I have been taking some Open University maths courses for fun, and to give myself the stick of assignments and deadlines to force me to learn some things I never formally did before.  It's been fun (mostly) and it's been useful for several reasons -- not just that I learned new things, but also because it has reminded me what it is actually like to be a student in terms of having particular assignments to do, exams to do, and even what interacting with a University from the other side is like.  Of course I did all that before, but interesting to do it again having seen life from the teaching side.  

This year, I had my final module for the MSc in Mathematics, which was the dissertation.  I wrote one on spline approximations to solutions of the Schrödinger equation, and I'm pleased to say that I passed and did just fine (getting a distinction, as I found out yesterday).  That means I can complete the story by attending a graduation ceremony from the other side, too.  I only managed to find a small picture of the gown I'll be entitled to wear, hence it looks a but blurry, but it's attached to this post.  Might be nice to wear this one at Surrey graduations for a bit of variation!



Monday, 14 July 2014

Nuclear Matters



So, after last week's NuSYM14 conference, it's back to to getting on with summer tasks in the office. I've spent the morning so far reading through a chapter of my students draft PhD thesis and giving comments, and I'm shortly going to meet a visitor of another mystery academic, who phoned me up to ask if I could help them with time-dependent density functional theory.  I don't know if I can, but I'll find out soon.  

The picture from the NuSYM conference was sent by the organisers to everyone that took part, and since it is going up on the conference web page anyway, I thought I'd reproduce it here, too.  If you want to see all the slides from all the talks, you can find them, too, on the conference web page.  In the picture, I'm in the panama hat, which unfortunately shades my face (although that's rather the point of it).

Speaking of nuclear matter, I've recently learnt of a conference going on in Kent this summer which includes at least one talk on nuclear matter -- specifically on its compressibility.  This conference is all about a model, known as Skyrmions, which are a field-theoretic approach to nuclei.  Typically, they are treated more as mathematical curiosities, or perhaps fairer to say are more studied by mathematical physicists and there's not much dialogue between them and people who style themselves nuclear physicists.  Too bad, really.  I don't think I'll make it to the Kent conference, but I never knew their model had got so far as to be applied to describing compressibility of nuclear matter, so will at least check out their work on it.


Tuesday, 8 July 2014

Dining on Hope

Later on this evening is the NuSYM14 conference dinner, in a fancy restaurant on Liverpool's Hope St.  Walking around there always makes me think of this song, with its obvious Liverpool connection:


Expected Liverpool

In a followup to my recent post, where I found myself making an unexpected trip to Liverpool, I can now report that I am deliberately in Liverpool, to attend the "4th International Symposium on the Nuclear Symmetry Energy NuSYM14".  The eponymous nuclear symmetry energy is the characteristic energy it takes to change protons to neutrons (or vice versa) in the nucleus.  More often than not, it's discussed in the context of infinite nuclear matterwhich is an idealised nucleus of infinite extent, which dispenses with difficult things like finite number of particles, and the complication of the surface of the nucleus.  It's an easy(ish) thing to model and calculate, and the symmetry energy can then be worked out by making calculations with different proportions on neutrons and protons in the nuclear matter.  

The conference symposium is about all the ways this fictitious system and its properties can be used as a proxy to link together a lot of actually observed things - like the properties of neutron stars, the properties of finite nuclei and the results of heavy-ion collisions.  It's a nice small-scale event (with about 50 people) and I gave a talk on Monday, which was about work that my BSc Final Year Project student did a few months ago.  That was about linking properties of the giant quadrupole resonance, in which real nuclei vibrate with a particular shape (going between stretched rugby ball and squashed Smartie) and nuclear matter.  We (or, in fact, James) found that these resonances seem to probe the derivative of the nuclear incompressibility.  The previous knowledge of this parameter of nuclear matter was very poor.

It's been nice to catch up with a bunch of people, and I've met a lot of new people too, since this is quite a genre-crossing field.

The conference is at the University of Liverpool.  We're in an old lecture theatre (but a perfectly fine one).  The coffee breaks are in the lobby of a new central lab teaching building, in which laboratory space for many disciplines has been put together in a shared facility.  It's probably the only building in the world where a room labelled "Radiation Laboratory" is opposite one labelled "Flint Knapping".  It also has an awesome vertical garden just outside it, shown in the picture.

Friday, 27 June 2014

Nuclear women in Bulgaria

One thing that my partner pointed out to me about the group of people attending this workshop in Bulgaria is that there are a lot of women present.  I guess it is true.  I had a look through the delegate list at the back of the booklet, and counted 27 male and 16 female attendees.  I don't know if that really counts as a lot, but it must say something about most physics gatherings she has been in that the group assembled here seemed out of the ordinary.  Good for Bulgaria!  The number of female nuclear theorists with permanent positions in Bulgaria (pop 7m, GDP USD0.1t) who are attending this small workshop is around the same as the number of nuclear theorists of both sexes in the entirety of the UK (pop 70m, GDP USD1.5t) with permanent positions.  

Anyway... A conference update:  I have generally enjoyed all the talks, but particularly I enjoyed learning a neat mathematical trick from Nikolay Minkov to do with factorising the Schrödinger equation in a way I will save describing further until I have successfully got mathjax working in Blogger.  I liked Xavier Viñas's work on attempting to write down a nuclear energy density functional based on a matching of a polynomial form of the density functional to give a realistic equations of state, with small additions to give good results for more or less all finite nuclei.  This is the sort of spirit in which energy density functionals should probably be used, rather than what I tend to do, starting from the Skyrme interaction.  It was nice to hear about a new facility being set up in Yerevan, in a talk by Roza Avetisyan.  A cyclotron mainly for medical isotope generation is being set up, with a beam line for nuclear physics experiments which will be a good place to train students in the arts of nuclear techniques, and some interesting ideas of reactions to look at were presented.

Yesterday saw our excursion day.  It was quite a long day, running from 9:15 to 19:15,  taking in a reconstituted Roman hill fort near Samokov, then lunch, then a tour round the Rila Monastery.  Alba, my 8mo daughter did an admirable job of coping with the long coach journey, the being carried round the sites, and the cabbage-rich lunch.  She continued to be a more or less welcome diversion to the other attendees, never getting to the stage of screaming constantly in a confined coach for hours on end, which would no doubt have changed other people's ideas about having babies as accompanying people at conferences...

The picture is a view from the hill fort.  Mostly, of course, it's just a tree.  You can see a bit of reconstructed wall, and some indication from the plain below of how high up we were.  The funicular was broken for the journey up, by the way, and pushing the pram up the path was hard work.  Special thanks to Rajdeep Chatterjee from Roorkee for helping here!

Monday, 23 June 2014

Rila, again

Like last year and the year before, I'm at the Nuclear Theory Workshop, organised by the group in Sofia, and held in a rustic hotel in the Rila Mountains.  It's day one, and I was scheduled to speak in the first session, like last year.  My talk followed talks by Andrzej Góźdź, and his student Aleksandra Pędrak (from Lublin, Poland) concerning collective Hamiltonians, and one by Attila Krasznahorkay (Debrecen, Hungary) on resonance states in calcium isotopes.  I enjoyed all the talks, and with Attila's experimental talk being relevant to things I can calculate, I got a few ideas of things to do.

My talk was a kind of advert for our recently-published computer code, Sky3D, with some details of the kind of physics problems one can solve with it -- quite a wide range from nuclear structure and dynamics -- and some technical details of implementation and usage.  I got a reasonable amount of interest out of the talk and a fair few questions.  Hopefully, having published the code, we'll get plenty of people interested in running it.  It's good to have given the talk on the first day, partly because now I can relax more and enjoy the other talks, and chatting to people, rather than tinkering with my talk, but also because there is now plenty of time for me to sit down with people and infect their computers with my code install my code on their computers.

This year, I brought travelling companions, as seen in the picture.  Eagle-eyed regular readers may notice that the mountains in the background haven't changed much, but the climbing frames in the playground have had a lick of paint.  My daughter Alba, in the picture, is a little young for the climbing frame, but she has already proved to be the star of the conference.  Her first plane journey went well,  It was on a pretty busy plane, and we had two seats in a group of three.  Our fellow passenger, seeing that he was sitting next to a family with an 8 month old baby graciously begged the stewardess to be allowed to sit elsewhere so as to give us a little more space.  We certainly didn't mind...